"Retina" is pretty much a marketing label, and I don't expect marketing labels to be scientifically precise. The point is that -- as Jakob Nielsen wrote in one of his Alertbox columns -- judging by 2013 standards, any computer screen below 200 ppi can nowadays be considered "lousy" (Nielsen's term), and us consumers should insist on computer manufacturers offering us 200+ ppi screens (at the very least that) as the new standard.

I'm sure that 326 ppi over 8 inches of an iPad mini screen, will be spectacular to behold -- whether technically "Retina" or not.